(Co)polycarbonate and process for producing the same

ABSTRACT

A processes for producing a (co)polycarbonate having a low terminal hydroxyl group concentration and being excellent in heat resistance and hue, which comprises melt-polycondensing a dihydroxy compound with a carbonic diester in the presence of a catalyst for transesterification selected from the group consisting of a nitrogen-containing basic compound, an alkali metal borate and an alkaline earth metal borate and in the presence of a specific ester compound. 
     A process for producing a linear, high-molecular weight (co)polycarbonate being excellent in heat resistance, hydrolysis resistance, hue and impact resistance which comprises melt-polycondensing a dihydroxy compound with a carbonic diester in the presence of a catalyst for transesterification selected from the group consisting of specific borates. 
     A process for producing a (co)polycarbonate being excellent in heat resistance, hydrolysis resistance, hue and impact resistance which comprises melt-polycondensing a dihydroxy compound with a carbonic diester in the presence of boric acid and/or ammonium hydrogenphosphite.

This is a division of Ser. No. 08/188,194, filed Jan. 28, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a (co)polycarbonate having a lowterminal hydroxyl group concentration which is obtained by adding anester compound in the melt-polycondensation of a dihydroxy compound witha carbonic diester in the presence of one or more catalysts selectedfrom among nitrogen-containing basic compounds, alkali metal borates andalkaline earth metal borates to thereby block the terminal hydroxylgroup (hydroxyl residue) of the thus formed (co)polycarbonate with anester group, and a process for producing the same.

The present invention also relates to a (co)polycarbonate compositioncomprising a borate and a linear, high-molecular weight(co)polycarbonate which is excellent in heat resistance, hydrolysisresistance, hue and impact resistance and which is obtained viapolycondensation of a dihydroxy compound with a carbonic diester in thepresence of a specific transesterification catalyst, and a process forproducing the same.

The present invention further relates to a (co)polycarbonate compositioncomprising boric acid and/or ammonium hydrogenphosphite and a(co)polycarbonate which is obtained via polycondensation of a dihydroxycompound with a carbonic diester in the presence of atransesterification catalyst, and a process for producing the same.

2. Description of the Related Art

A high-molecular-weight polycarbonate is a general-purpose engineeringthermoplastic which is useful in various fields, particularly asinjection molding material or sheet material substituting for windowpanes. It is said that the polycarbonate usually has excellent thermalresistance, transparency and impact resistance.

Generally known processes for producing a polycarbonate include, forexample, the phosgene process wherein a dihydroxy compound is reactedwith phosgene by interfacial polycondensation and thetransesterification process wherein a dihydroxy compound is reacted witha carbonic diester in a molten state.

The phosgene process, i.e., the interfacial polycondensation process, isgenerally effective in preparing a polycarbonate, but has disadvantagesthat the use of toxic phosgene is necessitated and that the formedpolycarbonate is contaminated with residual chloride ion.

In order to overcome these disadvantages, Japanese Patent Publication-ANo. 182336/1988 discloses a process for the preparation of apolycarbonate which comprises using liquid trichloromethylchloroformate, which is a dimer of phosgene, instead of the toxicphosgene and polycondensing it with a special dihydric phenol by theinterfacial process.

However, this patent document does not give any specific informationabout the special dihydric phenol with the exception of9,9-bis(4-hydroxyphenyl)fluorenes. Further, although Angew. Chem. 99,922(1987) describes that a polycarbonate is prepared from2,2-bis(4-hydroxyphenyl)propane by using triphosgene instead of thetoxic phosgene, a reaction mechanism wherein phosgene is generated isalso described therein.

A representative transesterification process comprises reacting adihydric phenol with a carbonic diester in the presence of atransesterification catalyst under heating under reduced pressure whiledistilling off a phenol formed to prepare a prepolymer and then reactingthe prepolymer under heating finally 290° C. or above in a high vacuumwhile distilling off a phenol formed to obtain a polycarbonate having ahigh molecular weight (see U.S. Pat. No. 4,845,062).

It is known that in the transesterification process, a prepolymer isprepared in an ordinary tank reactor having stirring blades in theinitial stage of the reaction and then the polycondensation reaction isconducted in, for example, a vented horizontal extruder in order toefficiently conduct the reaction to thereby obtain a polycarbonatehaving a high molecular weight.

However, the transesterification process has the problem that apolycarbonate having a high molecular weight has such an extremely highmelt viscosity unlike other engineering plastics that a temperature ashigh as 280° C. or above is necessitated for the reaction and so is ahigh vacuum (1 to 10⁻² Torr) for distilling off the monohydroxy compoundhaving a high boiling point formed, which makes the industrialization ofthe process difficult from the viewpoint of the equipment.

As examples of the polymerization catalysts to be used in the productionof polycarbonates by the transesterification process, hydroxides,hydrides, oxides, alcholates, carbonates and acetates of alkali metalsand alkaline earth metals are commonly cited. However, there is aproblem that these basic catalysts remain in the final products and thusseriously deteriorate the heat resistance, hydrolysis resistance,residence stability in the molding machine, weatherability and hue ofthe polycarbonates.

One method for solving these problems comprises adding a third componentto the reaction mixture to thereby weaken the effectiveness of the basiccatalysts. For example, DE Patent No. 1,031,512 (published on Jun. 4,1958) has disclosed that the above-mentioned problems can be avoided byadding a substance, which is capable of binding to a base, to a moltenresin at around the final point of the transesterification to therebyneutralize the basic catalyst. Further, Japanese Patent Publication-ANo. 175388/1992 has disclosed a method of adding an acidic compound to areaction product. However, these methods suffer from another problemthat a small amount of an additive can be hardly blended homogeneouslywith a resin of a high melt viscosity within a short period of time.

Another method for solving the above-mentioned problems comprisesaltering the type of the catalysts per se. For example, Japanese PatentPublication-B No. 20504/1971 has disclosed a method of addingtetrafluoroborate or hydroxyfluoroborate as the catalyst. However, thesecatalysts contain halogen atoms, which causes a fear of, for example,the corrosion of devices. Further, Japanese Patent Publication-A No.124934/1990 has disclosed that the above-mentioned decomposition, i.e.,the decomposition of the polycarbonate by heat, hydrolysis or the like,can be prevented by using a nitrogen-containing basic compound togetherwith an alkali metal (or alkaline earth metal) compound and boric acid(or an ester thereof). However, three compounds should be used as thepolymerization catalysts in this case, which makes this methodtroublesome. Furthermore, Japanese Patent Publication-A No. 51719/1985has disclosed a process for producing a polycarbonate having arelatively light-color with the use of a catalyst system comprising anitrogen-containing basic compound and a boric compound. However, thiscatalyst system exhibits low catalytic activity.

Accordingly, it has been urgently required to establish convenientprocesses for producing a polycarbonate having a low terminal hydroxylgroup concentration and a linear high-molecular weight polycarbonatewhich is excellent in heat resistance, hydrolysis resistance, hue andimpact resistance, via polycondensation of a dihydroxy compound with acarbonic diester in the presence of a transesterification catalyst.

DISCLOSURE OF THE INVENTION Summary of the Invention

The present inventors have found that a high-molecular weightpolycarbonate having a low terminal hydroxyl group concentration andbeing substantially free from chlorine ion can be obtained without usingtoxic phosgene by adding an ester compound in the step of Themelt-polycondensation of a carbonic diester with a dihydroxy compound,generally a dihydric phenol, which are used as compounds for forming acarbonate bond, in the presence of one or more compounds selected fromamong nitrogen-containing basic compounds, alkali metal borates andalkaline earth metal borates.

Accordingly, the first embodiment of the present invention relates to aprocess for producing a (co)polycarbonate which comprisesmelt-polycondensing a dihydroxy compound with a carbonic diester in thepresence of a catalyst for transesterification selected from the groupconsisting of a nitrogen-containing basic compound, an alkali metalborate and an alkaline earth metal borate and in the presence of anester compound represented by the formula: R_(a) COOR_(b) (wherein R_(a)represents a phenyl group which may be substituted with a straight-chainor branched alkyl group having 1 to 10 carbon atoms or an aryl grouphaving 8 to 12 carbon atoms; and R_(b) represents a phenyl group, astraight-chain or branched alkyl group having 1 to 10 carbon atoms or acyclic alkyl group having 3 to 8 carbon atoms).

The dihydroxy compound is generally a dihydric phenol, and preferablybisphenol A.

The ester compound represented by the formula: R_(a) COOR_(b) ispreferably one wherein R_(a) represents a phenyl group which may besubstituted with a branched alkyl group having 5 to 10 carbon atoms oran aryl group having 6 to 12 carbon atoms and R_(b) represents a phenylgroup, a branched alkyl group having 1 to 10 carbon atoms or a cyclicalkyl group having 8 to 8 carbon atoms, or another one wherein R_(a)represents a phenyl group which may be substituted with a methyl group,a tert-butyl group or an aryl group having 6 to 12 carbon atoms andR_(b) represents a phenyl group, a branched alkyl group having 1 to 10carbon atoms or a cyclic alkyl group having 8 to 8 carbon atoms, andstill preferably phenyl benzoate.

The ester compound represented by the formula R_(a) COOR_(b) is used inan amount of, per mol of the dihydroxy compound employed, preferablyfrom 10⁻⁴ to 10⁻² mol, still preferably from 10⁻⁴ to below 10⁻² mol, andespecially preferably from 10⁻³ to below 10⁻² mol.

The ester compound represented by the formula R_(a) COOR_(b) is added tothe reaction system preferably before the initiation of thepolycondensation or the initial stage of the polycondensation.

The second embodiment of the present invention relates to a(co)polycarbonate having a terminal blocked with an R_(a) CO group(wherein R_(a) is as defined above) and a terminal hydroxyl group.

The (co)polycarbonate is preferably one obtained by the processaccording to the first embodiment of the present invention.

Thus, the present invention includes a polycarbonate, which is obtainedby adding an ester compound represented by R_(a) COOR_(b) (wherein R_(a)represents a phenyl group or a phenyl group substituted with a branchedalkyl group having 5 to 10 carbon atoms or substituted with an arylgroup having 6 to 12 carbon atoms; and R_(b) represents a phenyl group,a branched alkyl group having 1 to 10 carbon atoms or a cyclic alkylgroup having 8 to 8 carbon atoms) in the melt-polycondensation of adihydric phenol with a carbonic diester in the presence of one or morecatalysts selected form among basic nitrogen compounds, i.e.,nitrogen-containing basic compounds, and alkali metal or alkaline earthmetal borates to thereby block the terminal hydroxyl group of the thusformed polycarbonate with an R_(a) CO group (wherein R_(a) is as definedabove), and a process for producing the same.

Further, the present inventors have found that the above-mentionedproblems accompanying the conventional art can be solved by using aborate as the polymerization catalyst. A comparison between borates withother basic compounds indicates that they are comparable to each otherin the effect of promoting transesterification but the use of theborates significantly suppresses the decomposition of polymers due toheat, water and the like, suggesting a large difference between thesesubstances. Thus it has been found that borates are highly useful as thepolymerization catalyst.

Thus, the third embodiment of the present invention relates to a processfor producing a (co)polycarbonate which comprises melt-polycondensing adihydroxy compound with a carbonic diester in the presence of a catalystfor transesterification selected from the group consisting of boratesrepresented by the following general formula: xM_(n) O.yB₂ O₃.zH₂)[wherein x is an integer of from 1 to 10; y is an integer of from 1 to10; z is 0 or an integer of from 1 to 10; n is 1 or 2; and M representsan alkali metal ion, an alkaline earth metal ion, a quaternary ammoniumion (NR₄ ⁺), a quaternary phosphonium ion (PR₄ ⁺) or a tertiarysulfonium ion (R₃ S⁺) (wherein R represents a hydrogen atom, astraight-chain or branched alkyl group or an aromatic group which may besubstituted)].

The borates to be used in the present invention are those represented bythe formula: xM_(n) O.yB₂ O₃.zH₂ O and the M in the formula representspreferably an alkali metal ion, an alkaline earth metal ion or aquaternary ammonium ion, still preferably an alkali metal ion, andespecially preferably a sodium ion, or a lithium ion or a potassium ion.

The borate is preferably used in an amount of from 10⁻⁸ to 10⁻¹ mol permol of the dihydroxy compound.

The polycondensation is preferably conducted in the presence of,further, an electron donor amine compound as a transesterificationcatalyst and the amount of the electron donor amine compound to be usedis preferably from 10⁻⁵ to 10⁻¹ mol per mol of the dihydroxy compound.

Thus, the third embodiment of the present invention includes a processfor producing a polycarbonate characterized in that in themelt-polycondensation of a dihydroxy compound with a carbonic diester toproduce a polycarbonate, a borate represented by the following generalformula:

    xM.sub.n O.yB.sub.2 O.sub.3.zH.sub.2 O

(wherein x is an integer of from 1 to 10; y is an integer of from 1 to10; z is an integer of from 0 to 10; n is an integer of from 1 to 2; andM represents an alkali metal, an alkaline earth metal, a quaternaryammonium, a quaternary phosphonium or a tertiary sulfonium, preferablyan alkali metal, an alkaline earth metal or a quaternary ammonium) isused optionally together with an electron donor amine compound as atransesterification catalyst(s).

The fourth embodiment of the present invention relates to a(co)polycarbonate composition comprising a (co)polycarbonate and aborate represented by the following general formula: xM_(n) O.yB₂ O₃.zH₂O (wherein x, y, z, n and M are as defined above).

The (co)polycarbonate composition is preferably one obtained by theprocess according to the third embodiment of the present invention.

Furthermore, the present inventors have found that the above-mentionedproblems accompanying the conventional art can be solved by using boricacid and/or ammonium hydrogenphosphite in the transesterification.

Thus, the fifth embodiment of the present invention relates to a processfor producing a (co)polycarbonate which comprises melt-polycondensing adihydroxy compound with a carbonic diester in the presence of boric acidand/or ammonium hydrogenphosphite.

The boric acid and/or ammonium hydrogenphosphite is preferably added tothe reaction system before the initiation of the polycondensation or theinitial stage of the polycondensation.

The polycondensation is generally conducted in the presence of, further,a basic catalyst for transesterification, and the basic catalyst ispreferably a metal salt of boric acid, a nitrogen-containing basiccompound, an electron donor amine compound or a salt of an electrondonor amine compound. Alternatively, the basic catalyst is preferably acompound selected form the group consisting of an alkali metal compoundand an alkaline earth metal compound. Further, the basic catalyst may bea mixture of a nitrogen-containing basic compound and a compoundselected form the group consisting of an alkali metal compound and analkaline earth metal compound.

The sixth embodiment of the present invention relates to a(co)polycarbonate composition comprising a (co)polycarbonate and, boricacid and/or ammonium hydrogenphosphite. The (co)polycarbonatecomposition generally comprises a (co)polycarbonate, a basic compound,i.e., a basic catalyst, and, boric acid and/or ammoniumhydrogenphosphite.

The (co)polycarbonate composition preferably comprises a(co)polycarbonate, a metal salt of boric acid and, boric acid and/orammonium hydrogenphosphite, wherein the total amount of the boron atomof the boric acid and the phosphorus atom of the ammoniumhydrogenphosphite is 0.01 to 500 times, advantageously 1 to 500 timesand still advantageously 5 to 200 times by mol the amount of the metalatom of the metal salt of boric acid.

The (co)polycarbonate composition preferably comprises a(co)polycarbonate, a nitrogen-containing basic compound and, boric acidand/or ammonium hydrogenphosphite, wherein the total amount of the boronatom of the boric acid and the phosphorus atom of the ammoniumhydrogenphosphite is 0.01 to 500 times and advantageously 0.01 to 10times by mol the amount of the basic group of the nitrogen-containingbasic compound.

The (co)polycarbonate composition preferably comprises a(co)polycarbonate, a compound selected form the group consisting of analkali metal compound and an alkaline earth metal compound and, boricacid and/or ammonium hydrogenphosphite, wherein the total amount of theboron atom of the boric acid and the phosphorus atom of the ammoniumhydrogenphosphite is 0.01 to 500 times, preferably 1 to 500 times andstill preferably 5 to 200 times by mol that of the metal atoms of thealkali metal compound and the alkaline earth metal compound.

The (co)polycarbonate composition preferably comprises a(co)polycarbonate, a nitrogen-containing basic compound, a compoundselected from the group consisting of an alkali metal compound and analkaline earth metal compound and, boric acid and/or ammoniumhydrogenphosphite, wherein the total amount of the boron atom of theboric acid and the phosphorus atom of the ammonium hydrogenphosphite is0.01 to 500 times by mol that of the basic group of thenitrogen-containing basic compound and the metal atoms of the alkalimetal compound and the alkaline earth metal compound.

Furthermore, the (co)polycarbonate composition is preferably oneobtained by the process according to the fifth embodiment of the presentinvention.

Further scope and the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

DETAILED DESCRIPTION OF THE INVENTION

Now, the monomers to be used as the raw materials in the presentinvention will be described.

As representative examples of the carbonic diester to be used in thepresent invention, diphenyl carbonate, ditolyl carbonate,bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate,bis(diphenyl) carbonate, diethyl carbonate, dimethyl carbonate, dibutylcarbonate and dicyclohexyl carbonate are cited. Among these compounds,diphenyl carbonate is a particularly preferable one.

As representative examples of the dihydroxy compound to be used in thepresent invention, dihydric phenols are cited, and a phenolic compoundselected from the group consisting of compounds represented by thefollowing general formulas (1), (2), (3) and (4) is preferably used:##STR1## wherein R₁, R₂, R₃, R₄ and R₅ each represents a straight-chainor branched alkyl group having 1 to 8 carbon atoms or a phenyl group, Xrepresents a halogen atom, n represents 0 or an integer of 1 to 4, and mrepresents an integer of 1 to 4.

As examples of bisphenols classified into the group represented by thegeneral formula (1), bisphenol A [2,2-bis(4-hydroxyphenyl)propane],2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)-4-methylpentane,2,2-bis(4-hydroxyphenyl)octane, 4,4'-dihydroxy-2,2,2-triphenylethane and2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane may be cited.

As examples of bisphenols classified into the group represented by thegeneral formula (2), 2,2-bis(4-hydroxy-3-methylphenyl)propane,2,2-bis(4-hydroxy-3-isopropylphenyl)propane,2,2-bis(4-hydroxy-3-secbutylphenyl)propane,2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane and2,2-bis(4-hydroxy-3-tert-butylphenyl)propane may be cited.

As examples of bisphenols classified into the group represented by thegeneral formula (3), those represented by the following general formula(3') are preferable: ##STR2## wherein R₄ is as defined above.

Examples of bisphenols classified into the group represented by thegeneral formula (8) include1,1'-bis(4-hydroxyphenyl)-p-diisopropylbenzene and1,1'-bis(4-hydroxyphenyl)-m-diisopropylbenzene.

As an example of bisphenols classified into the group represented by thegeneral formula (4), 1,1-bis(4-hydroxyphenyl)cyclohexane may be cited.

Furthermore, a (co)polycarbonate can be produced by combining two ormore dihydric phenols selected from among those represented by thegeneral formulas (1) to (4).

Next, the first and second embodiments of the present invention will bedescribed.

Representative examples of the nitrogen-containing basic compound usablein the present invention include ammonium hydroxides having an alkylgroup, an aryl group and/or an alkylaryl group, such astetramethylammonium hydroxide (Me₄ NOH), tetraethylammonium hydroxide(Et₄ NOH), tetrabutylammonium hydroxide (Bu₄ NOH) andtrimethylbenzylammonium hydroxide [C₆ H₅ -CH₂ (Me)₃ NOH]; tertiaryamines such as trimethylamine, triethylamine, dimethylbenzylamine andtriphenylamine; secondary amines represented by R₂ NH (wherein Rrepresents an alkyl group such as a methyl group and an ethyl group, oran aryl group such as a phenyl group and a tolyl group): primary aminesrepresented by RNH₂ (wherein R is as defined above): and basic saltssuch as ammonia, tetramethylammonium borohydride (Me₄ NBH₄),tetrabutylammonium borohydride (Bu₄ NH₄), tetrabutylammoniumtetraphenylborate (Bu₄ NBPh₄) and tetramethylammonium tetraphenylborate(Me₄ NBPh4).

Additional examples thereof include 4-(4-methyl-1-piperidinyl)pyridine,N,N-dimethyl-4-aminopyridine, 4-diethylaminopyridine,4-pyrrolidinopyridine, 4-aminopyridine, 2-aminopyridine,2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine,4-hydroxypyridine, 2-dimethylaminoimidazole, 2-methoxyimidazole,2-mercaptoimidazole, aminoquinoline, benzimidazole, imidazole,2-methylimidazole, 4-methylimidazole, diazabicyclooctane (DABCO),1,8-diazabicyclo[5.4.0]-7-undecene (DBU) and4-(4-methylpyrrolidinyl)pyridine.

Representative examples of the alkali metal borates and alkaline earthmetal borates include sodium diborate, sodium tetraborate, sodiumpentaborate, sodium hexaborate, sodium octaborate, lithium metaborate,lithium tetraborate, lithium pentaborate, potassium metaborate,potassium tetraborate, potassium pentaborate, potassium hexaborate,potassium octaborate, ammonium metaborate, ammonium tetraborate,ammonium pentaborate, ammonium octaborate, ammonium borate,tetramethylammonium borate, aluminum potassium borate, cadmium borate,silver borate, copper borate, lead borate, nickel borate, magnesiumborate and manganese borate.

These transesterification catalysts may be used either singly orcombinedly in the first embodiment of the present invention. Thecatalyst(s) may be added either at once at the feeding of the monomersor in portions during the reaction.

It is required to use the transesterification catalyst in an amount offrom 10⁻⁸ to 10⁻¹ mol, preferably from 10⁻⁷ to 10⁻² mol, per mol of thedihydroxy compound fed in the reaction system. When the amount of thetransesterification catalyst is smaller than 10⁻⁸ mol, only a poorcatalytic action is achieved, thus resulting in a slow polymerizationrate. When it is used in an amount exceeding 10⁻¹ mol, the catalystremains at a higher ratio in the reaction mixture comprising a(co)polycarbonate, which deteriorates the physical properties of the(co)polycarbonate.

The process of the first embodiment of the present invention isconducted by adding an ester compound represented by the formula: R_(a)COOR_(b) (wherein R_(a) represents a phenyl group which may besubstituted with a straight-chain or branched alkyl group having 1 to 10carbon atoms or which may be substituted with an aryl group having 8 to12 carbon atoms: and R_(b) represents a phenyl group, a straight-chainor branched alkyl group having 1 to 10 carbon atoms or a cyclic alkylgroup having 8 to 8 carbon atoms) in the melt-polycondensation of adihydroxy compound such as bisphenol A with a carbonic diester with theuse of one or more catalysts selected from the group consisting of anitrogen-containing basic compound, an alkali metal borate and analkaline earth metal borate.

As examples of the ester compound represented by the formula: R_(a)COOR_(b), phenyl benzoate, phenyl p-methylbenzoate and phenylp-tert-butylbenzoate may be cited. Among these compounds, phenylbenzoate is a particularly preferable one.

When the polymerization is effected in a high vacuum, an ester compoundrepresented by the formula: R_(c) COOR_(b) (wherein R_(c) is a loweralkyl group and R_(b) is as defined above) would be distilled off fromthe system because R_(c) is a lower alkyl group. In contrast, an estercompound represented by the formula: R_(a) COOR_(b) (wherein R_(a) andR_(b) are as defined above), which is used in the present invention,would not be distilled off from the system in such a case because R_(a)is a phenyl group which may be substituted. Further, the ester compoundrepresented by the formula: R_(a) COOR_(b) (wherein R_(a) and R_(b) areas defined above) gives a thermally stable ester bond in the(co)polycarbonate thus formed.

This ester compound is added in the reaction system in an amount ofpreferably from 10⁻⁴ to 10⁻² mol, still preferably from 10⁻⁴ to below10⁻² mol and especially preferably from 10⁻³ to below 10⁻² mol per molof the dihydroxy compound to be used. When the amount of the estercompound exceeds 10⁻² mol, the molecular weight of the (co)polycarbonateto be formed is reduced. By blocking the terminal hydroxyl group of thethus formed (co)polycarbonate with an R_(a) CO group (wherein R_(a) isas defined above) by adding the ester compound represented by theformula: R_(a) COOR_(b) (wherein R_(a) and R_(b) are as defined above)in the reaction system, a (co)polycarbonate being excellent in heatresistance and hue can be obtained. The ester compound is added to thereaction system preferably before the initiation of the polycondensationor the initial stage of the polycondensation.

The process for producing a (co)polycarbonate according to the firstembodiment of the present invention will be described hereinafter ingreater detail. First, the reaction temperature ranges from 100° toabout 300° C., preferably from 130° to 280° C. A reaction temperaturelower than 130° C. results in a slow reaction rate, while one exceeding800° C. enhances the tendency toward the occurrence of side reactions.The pressure in the reactor in the reaction ranges from atmosphericpressure to 0.1 Torr. When this pressure is excessively high, themonohydroxy compound formed as a side product cannot be efficientlyeliminated. When the pressure is excessively low, on the other hand, thecarbonic diester and/or dihydroxy compound employed as monomers would bedistilled off and the molar ratio of the reactive terminals of themonomers is consequently changed, which makes it difficult to obtain ahigh-molecular weight (co)polycarbonate. To suppress the distillation ofthe monomers, it is preferable that the initial polycondensation reactorbe provided with a rectification column.

As the material of the polycondensation reactor, those generally used inchemical devices such as stainless steel are usable. In order to obtainan uncolored, high-molecular weight resin, it is preferable that atleast 60% of the material where the reaction mixture comes into contactwith, i.e., the material constituting the inner surface of the reactor,comprises one or more materials selected from among nickel, chromium andglass.

The carbonic diester should be used at least in an amount equimolar tothe dihydroxy compound. In general, 1 mol of a carbonate compound, i.e.,the carbonic diester, should react with 1 mol of a dihydroxy compound inorder to form a high-molecular weight (co)polycarbonate. When bisphenyl(or diphenyl) carbonate is used as the carbonic diester, 2 mol of phenolis formed by the above-mentioned reaction and distilled off from thereaction system. Although the ester compound is used in the firstembodiment of the present invention in order to minimize the terminalhydroxyl group concentration of the (co)polycarbonate to therebyeliminate undesirable effects on the physical properties of the(co)polycarbonate, in particular heat resistance and hue, due to theterminal hydroxyl groups, the molar ratio of the carbonic diester to thedihydroxy compound is also important to minimize the terminal hydroxylgroup concentration of the (co)polycarbonate. It is desirable to use thecarbonic diester in an amount of from 1.01 to 1.20 mol per mol of thedihydroxy compound.

Definitely, the terminal hydroxyl group concentration of the(co)polycarbonate prepared according to the first embodiment of thepresent invention or the (co)polycarbonate according to the secondembodiment of the present invention ranges preferably from 8 to 30% bymol, still preferably from 10 to 30% by mol. When a terminal hydroxylconcentration is less than 8% by mol, the (co)polycarbonate usually hasa reduced molecular weight. When a terminal hydroxyl concentrationexceeds 30% by mol, the (co)polycarbonate usually has a deterioratedheat stability. The term "terminal hydroxyl group concentration" meansthe ratio of the terminal hydroxyl groups to all the terminal groups inthe (co)polycarbonate.

The viscosity-average molecular weight (Mv) of the (co)polycarbonateprepared according to the first embodiment of the present invention orthe (co)polycarbonate according to the second embodiment of the presentinvention ranges from 10,000 to 100,000, preferably from 18,000 to70,000. The hue value thereof is about 0.2 or below, preferably about0.1 or below. The viscosity-average molecular weight (Mv) is determinedfrom the limiting viscosity number [η] of the solution of the reactionmixture comprising the (co)polycarbonate in methylene chloride. The huevalue is a difference (A₃₈₀ -A₅₈₀) in the absorbances of a 10 wt. %solution of the reaction mixture comprising the (co)polycarbonate inmethylene chloride at 380 nm and 580 nm determined by UV spectrometry.

Next, the third and fourth embodiments of the present invention will bedescribed.

Representative examples of the borates represented by the formula:xM_(n) O.yB₂ O₃.zH₂ O (wherein x, y, z, n and M are as defined above)and used as a transesterification catalyst in the third embodiment ofthe present invention include sodium diborate, sodium tetraborate,sodium pentaborate, sodium hexaborate, sodium octaborate, lithiummetaborate, lithium tetraborate, lithium pentaborate, potassiummetaborate, potassium tetraborate, potassium pentaborate, potassiumhexaborate, potassium octaborate, ammonium metaborate, ammoniumtetraborate, ammonium pentaborate, ammonium octaborate, ammonium borate,tetramethylammonium borate, aluminum potassium borate, cadmium borate,silver borate, copper borate, lead borate, nickel borate, magnesiumborate and manganese borate. Among them, alkali metal borates arepreferable, sodium borate is still preferable, and lithium borate andpotassium borate are especially preferable.

Representative examples of the electron donor amine compound usable inthe third embodiment of the present invention includeN,N-dimethyl-4-aminopyridine (4-dimethylaminopyridine),4-diethylaminopyridine, 4-pyrrolidinopyridine, 4-aminopyridine,2-hydroxypyridine, 4-hydroxypyridine, 2-methoxypyridine,4-methoxypyridine, 2-methoxyimidazole, 1-methylimidazole, imidazole,aminoquinoline, 4-methylimidazole and diazabicyclooctane (DABCO).

A borate or plural borates may be used, and an electron donor aminecompound or plural electron donner amine compounds may be used in thethird embodiment of the present invention. A borate may be used or acombination of a borate with an electron donor amine compound may beused. The catalyst(s) may be added either at once at the feeding of themonomers or in portions during the reaction.

It is required to use the borate in an amount of from 10⁻⁸ to 10⁻¹ mol,preferably from 10⁻⁷ to 10⁻² mol, per mol of the dihydroxy compound fedin the reaction system. When the amount of the borate is smaller than10⁻⁸ mol, only a poor catalytic action is achieved, thus resulting in aslow polymerization rate. When it is used in an amount exceeding 10⁻¹mol, the catalyst remains at a higher ratio in the reaction mixturecomprising a (co)polycarbonate, which deteriorates the physicalproperties of the (co)polycarbonate.

It is required to use the electron donor amine compound in an amount offrom 10⁻⁵ to 10⁻¹ mol, preferably from 10⁻⁴ to 10⁻² mol, per tool of thedihydroxy compound fed in the reaction system. When the amount of theelectrons donor amine compound is smaller than 10⁻⁵ mol, only a poorcatalytic action is achieved, thus resulting in a slow polymerizationrate. When it is used in an amount exceeding 10⁻¹ mol, the catalystremains at a higher ratio in the reaction mixture comprising a(co)polycarbonate, which deteriorates the physical properties of the(co)polycarbonate.

The process for producing a (co)polycarbonate according to the thirdembodiment of the present invention will be described hereinafter ingreater detail. First, the reaction temperature ranges from 100° toabout 300° C., preferably from 180° to 280° C. A reaction temperaturelower than 130° C. results in a slow reaction rate, while one exceeding300° C. enhances the tendency toward the occurrence of side reactions.The pressure in the reactor in the reaction ranges from atmosphericpressure to 0.1 Torr. When this pressure is excessively high, themonohydroxy compound formed as a side product cannot be efficientlyeliminated. When the pressure is excessively low, on the other hand, thecarbonic diester and/or dihydroxy compound employed as monomers would bedistilled off and the molar ratio of the reactive terminals of themonomers is consequently changed, which makes it difficult to obtain ahigh-molecular weight (co)polycarbonate. To suppress the distillation ofthe monomers, it is preferable that the initial polycondensation reactorbe provided with a rectification column.

As the material of the polycondensation reactor, those generally used inchemical devices such as stainless steel are usable. In order to obtainan uncolored, high-molecular weight resin, it is preferable that atleast 60% of the material where the reaction mixture comes into contactwith, i.e., the material constituting the inner surface of the reactor,comprises one or more materials selected from among nickel, chromium andglass.

The carbonic diester should be used at least in an amount equimolar tothe dihydroxy compound. In general, 1 mol of a carbonate compound, i.e.,the carbonic diester, should react with 1 mol of a dihydroxy compound inorder to form a high-molecular weight (co)polycarbonate. When bisphenyl(or diphenyl) carbonate is used as the carbonic diester, 2 mol of phenolis formed by the above-mentioned reaction and distilled off from thereaction system. However, the carbonic diester is used in an amount of1.01 to 1.5 mol, preferably 1.015 to 1.20 mol based on 1 mol of thedihydroxy compound because the carbonic diester as the monomer issometimes distilled off with the removal of the monohydroxy compoundformed as a by-product.

In the third embodiment of the present invention, it is also possiblethat a carbonic diester compound, an ester compound or a phenol compoundis added to the reaction system as a terminal-blocking agent in theabove preparation of a (co)polycarbonate from the dihydroxy compound andthe carbonic diester in the presence of the transesterificationcatalyst. The amount of the blocking agent to be used is 0.05 to 10 mole%, preferably 1 to 5 mole % based on the amount of the dihydriccompound.

It is thought that the catalyst(s) used remains as such in the reactionmixture obtained, therefore the (co)polycarbonate composition, i.e., thereaction mixture, obtained by the third embodiment of the presentinvention comprises a (co)polycarbonate, a borate represented by thefollowing general formula: xM_(n) O.yB₂ O₃.zH₂ O (wherein x, y, z, n andM are as defined above) and optionally an electron donor amine compound.Similarly, the (co)polycarbonate composition of the fourth embodiment ofthe present invention comprises a (co)polycarbonate, a boraterepresented by the following general formula: xM_(n) O.yB₂ O₃.zH₂ O(wherein x, y, z, n and M are as defined above) and optionally anelectron donor amine compound.

Further, the fifth and sixth embodiments of the present invention willbe described.

The boric acid includes orthoboric acid, metaboric acid, tetraboric acidand the like.

The boric acid and the ammonium hydrogenphosphite are acidic substancesand used to neutralize a basic catalyst in the fifth embodiment of thepresent invention. The acidic substance may be added in the reactionsystem at any time. However, the acidic substance is preferably added inthe reaction system before the reaction system becomes viscous in orderto mix the acidic substance with other components such as startingmonomers homogeneously. That is, the acidic substance is preferablyadded to the reaction system before the initiation of thepolycondensation or the initial stage of the polycondensation.

In the fifth embodiment of the present invention, a basictransesterification catalyst is used. Examples of the basictransesterification catalyst include metal salts of boric acid,nitrogen-containing basic compounds, electron amine compounds, salts ofthe electron amine compounds, alkali metal compounds and alkaline earthmetal compounds.

Examples of the metal salts of boric acid include those described asrepresentative examples of the borates with respect to the thirdembodiment of the present invention. Examples of the nitrogen-containingbasic compounds include those described as representative examples ofthe nitrogen-containing basic compound with respect to the firstembodiment of the present invention.

Examples of the electron donor amine compounds include those describedas representative examples of the electron donor amine compounds withrespect to the third embodiment of the present invention. Examples ofthe salts of the electron donor amine compounds include borates,acetates, formates, nitrates, nitrites, oxalates, sulfates, phosphates,fluoroborates and hydrogenborates of the above described electron donoramine compounds.

Examples of the alkali metal compounds include sodium hydroxide, lithiumhydroxide, potassium hydroxide, sodium hydrogencarbonate, lithiumhydrogencarbonate, potassium hydrogencarbonate, sodium carbonate,lithium carbonate, potassium carbonate, sodium acetate, lithium acetate,potassium acetate, sodium stearate, lithium stearate, potassiumstearate, sodium borate, lithium borate, potassium borate, sodiumborohydride, lithium borohydride, potassium borohydride, sodiumborophenylate, sodium benzoate, lithium benzoate, potassium benzoate,disodium hydrogenphosphate, dilithium hydrogenphosphate, dipotassiumhydrogenphosphate, disodium salt of bisphenol A, dilithium salt ofbisphenol A, dipotassium salt of bisphenol A, sodium phenolate, lithiumphenolate and potassium phenolate.

Examples of the alkaline earth metal compounds include barium hydroxide,calcium hydroxide, magnesium hydroxide, strontium hydroxide, bariumhydrogencarbonate, calcium hydrogencarbonate, magnesiumhydrogencarbonate, strontium hydrogencarbonate, barium carbonate,calcium carbonate, magnesium carbonate, strontium carbonate, bariumacetate, calcium acetate, magnesium acetate, strontium acetate, bariumstearate, calcium stearate, magnesium stearate, strontium stearate andmagnesium borate.

The basic catalyst may be used either singly or combinedly. Thecatalyst(s) may be added either at once at the feeding of the monomersor in portions during the reaction.

It is required to use the metal salt of boric acid, alkali metalcompound or alkaline earth metal compound in an amount of from 10⁻⁸ to10⁻¹ mol, preferably from 10⁻⁷ to 10⁻² mol, per mol of the dihydroxycompound fed in the reaction system. When the amount is smaller than10⁻⁸ mol, only a poor catalytic action is achieved, thus resulting in aslow polymerization rate. When it is used in an amount exceeding 10⁻¹mol, the catalyst remains at a higher ratio in the reaction mixturecomprising a (co)polycarbonate, which deteriorates the physicalproperties of the (co)polycarbonate.

It is required to use the nitrogen-containing basic compound includingthe electron donor amine compound in an amount of from 10⁻⁵ to 10⁻¹ mol,preferably from 10⁻⁴ to 10⁻² mol, per mol of the dihydroxy compound fedin the reaction system. When the amount is smaller than 10⁻⁵ mol, only apoor catalytic action is achieved, thus resulting in a slowpolymerization rate. When it is used in an amount exceeding 10⁻¹ mol,the catalyst remains at a higher ratio in the reaction mixturecomprising a (co)polycarbonate, which deteriorates the physicalproperties of the (co)polycarbonate.

In the fifth embodiment of the present invention, the basic catalyst andthe acidic substance are employed such a ratio that (1) the total amountof the boron atom of the boric acid and the phosphorus atom of theammonium hydrogenphosphite is 0.01 to 500 times, preferably 1 to 500times and still preferably 5 to 200 times by mol the amount of the metalatom of the metal salt of boric acid, that (2) the total amount of theboron atom of the boric acid and the phosphorus atom of the ammoniumhydrogenphosphite is 0.01 to 500 times, preferably 0.01 to 10 times, bymol the amount of the basic group of the nitrogen-containing basiccompound, that (8) the total amount of the boron atom of the boric acidand the phosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500times, preferably 1 to 500 times and still preferably 5 to 200 times, bymol that of the metal atoms of the alkali metal compound and thealkaline earth metal compound or that (4) the total amount of the boronatom of the boric acid and the phosphorus atom of the ammoniumhydrogenphosphite is 0.01 to 500 times by mol that of the basic group ofthe nitrogen-containing basic compound and the metal atoms of the alkalimetal compound and the alkaline earth metal compound. Needless to say,when only one acidic substance, i.e., boric acid or ammoniumhydrogenphosphite, is employed, "the total amount of the boron atom ofthe boric acid and the phosphorus atom of the ammoniumhydrogenphosphite" in the above items (1) to (4) means "the amount ofthe boron atom of the boric acid" or "the amount of the phosphorus atomof the ammonium hydrogenphosphite".

It is thought that the catalyst(s) and acidic substance(s) used remainas such in the reaction mixture, therefore the (co)polycarbonatecomposition, i.e., the reaction mixture, obtained by the fifthembodiment of the present invention comprises a (co)polycarbonate, acatalyst and an acidic substance.

It is also thought that the ratio between the amounts of the catalystand the acidic substance in the (co)polycarbonate composition, i.e., thereaction mixture, obtained by the fifth embodiment of the presentinvention is the same as that of employed, i.e., the ratio between theamounts of the catalyst and the acidic substance fed.

The process for producing a (co)polycarbonate according to the fifthembodiment of the present invention is the same as that of the thirdembodiment of the present invention, except that an acidic substance isused and the kind of the catalyst is not limited.

The (co)polycarbonate composition of the sixth embodiment of the presentinvention comprises a (co)polycarbonate, a catalyst and an acidicsubstance. The ratio between the amounts of the catalyst and the acidicsubstance in the (co)polycarbonate composition of the sixth embodimentof the present invention is preferably as follows:

(1) the total amount of the boron atom of the boric acid and thephosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times,preferably 1 to 500 times and still preferably 5 to 200 times, by molthe amount of the metal atom of the metal salt of boric acid,

(2) the total amount of the boron atom of the boric acid and thephosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times,preferably 0.01 to 10 times by mol the amount of the basic group of thenitrogen-containing basic compound,

(3) the total amount of the boron atom of the boric acid and thephosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times,preferably 1 to 500 times and still preferably 5 to 200 times, by molthat of the metal atoms of the alkali metal compound and the alkalineearth metal compound, or

(4) the total amount of the boron atom of the boric acid and thephosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 timesby mol that of the basic group of the nitrogen-containing basic compoundand the metal atoms of the alkali metal compound and the alkaline earthmetal compound.

The acidic substance neutralizes the basic catalyst and thereforereduces the unfavorable influences which may be caused by the basiccatalyst remaining in the reaction mixture.

EXAMPLES

The present invention will now be described in more detail withreference to the following Examples which should not be considered tolimit the scope of the present invention.

First, a description will be made on the methods for the determinationsand evaluations of the hue, viscosity-average molecular weight (Mv),terminal hydroxyl group concentration based on all the terminal groupsand glass transition point, and the heat aging tests (storage stabilitytests) and hydrolysis test described in the following Examples andComparative Examples.

Hue:

The hue was evaluated by determining a difference (A₃₈₀ -A₅₈₀) in theabsorbances of a 10 wt. % solution of the reaction mixture comprisingthe (co)polycarbonate in methylene chloride at 880 nm and 580 nm by UVspectrometry.

Viscosity-average molecular weight (Mv):

The limiting viscosity number [η] of the solution of the reactionmixture comprising the (co)polycarbonate in methylene chloride wasdetermined with an Ubbelohde's viscometer at 20° C. The concentration ofthe reaction mixture in the solution was 0.5 g/dl. The viscosity-averagemolecular weight of the (co)polycarbonate was calculated from thelimiting viscosity number [η] determined according to the followingformula:

    [η]=1.11×10.sup.-4 Mv.sup.0.82

Terminal hydroxyl group concentration of the (co)polycarbonate based Onall the terminal groups thereof:

The reaction mixture comprising the (co)polycarbonate was dissolved inheavy chloroform to prepare a 5 wt. % solution thereof. The terminalhydroxyl group concentration was determined with the solution accordingto ¹³ C-NMR spectrometry.

Glass transition point:

Glass transition point was measured with the use of differentialscanning calorimeter (Perkin-Elmer 2C).

Heat aging test:

(a) Number of cleavages

A test piece was prepared by pressing the reaction mixture comprisingthe (co)polycarbonate in a molten state and allowed to stand in an ovenat 160° C. for 10, 20 or 80 days. Then the molecular weight loss wasevaluated based on the number of cleavages of the (co)polycarbonate,i.e., (Mv₀ /Mv_(t)) minus 1 (wherein Mv₀ represents theviscosity-average molecular weight of the (co)polycarbonate constitutingthe test piece before the initiation of the test and Mv_(t) the one tdays after the initiation of the test). The process for determining theviscosity-average molecular weight was the same as that described above.A number of cleavages of 1.0 means that each polymer chain of the(co)polycarbonate has been cleaved once on average and thus the(co)polycarbonate is halved in molecular weight.

(b) Hue

The hue (YI) of each reaction mixture comprising the (co)polycarbonatewas determined on a color difference meter (mfd. by Nippon Denshoku,300A) by the use of a sheet [50×50×2 mm (H-W-D)] prepared by the hotpressing quenching process, before and after storage at 160° C. for 720hours.

Hydrolysis test:

A test piece was prepared in the same manner as that employed in theabove heat aging test (a). After allowing to stand at 100° C. under 100%RH for 10 days, the molecular weight loss is evaluated based on thenumber of cleavages in the same manner as that employed in the aboveheat aging test (a).

Example I-1

Into a nickel-lined Tank reactor were fed 4580 g (20 mol) of bisphenol A[2,2-bis-(4-hydroxyphenyl)propane], 4391.5 g (20.5 mol) of diphenylcarbonate, 489 mg (4×10⁻³ mol) of N,N-dimethyl-4-aminopyridine and 19.8g (0.1 mol) of phenyl benzoate. After melting at 180° C. and stirringfor 1 hour in a nitrogen atmosphere, The mixture was heated while slowlyreducing the pressure until The temperature and the pressure finallyreached respectively 270° C. and 1.1 Torr and polycondensation waseffected for 4 hours under stirring under those conditions with theremoval of formed phenol by distillation. The reaction mixture wasfurther reacted in a vertical, double-screw, self-cleaning reactor under0.1 Torr and 280° C. for 50 minutes with The removal of formed phenol.Thus a colorless and transparent reaction mixture comprising apolycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of The reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 28,000and a terminal hydroxyl group concentration of 28 molar % based on allthe terminal groups of The polycarbonate, which was calculated by usingthe amounts of phenolic Terminals and phenyl Terminals determined by ¹³C-NMR spectroscopy.

Example I-2

A polycondensation was effected under the same conditions as thoseemployed in Example I-1 except that 29 mg (1.44×10⁻⁴ mol) of sodiumtetraborate was used as the transesterification catalyst instead of theN,N-dimethyl-4-aminopyridine. Thus a colorless and transparent reactionmixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.10. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 29,000and a terminal hydroxyl group concentration of 19 molar % based on allthe terminal groups of the polycarbonate.

Example I-3

A polycondensation was effected under the same conditions as thoseemployed in Example I-1 except that 29 mg (1.44×10⁻⁴ mol) of sodiumtetraborate and 48.9 mg (4×10⁻⁴ mol) of N,N-dimethyl-4-aminopyridinewere used as the transesterification catalysts instead of 489 mg of theN,N-dimethyl-4-aminopyridine. Thus a colorless and transparent reactionmixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (My) of 82,000and a terminal hydroxyl group concentration of 20 molar % based on allthe terminal groups of the polycarbonate.

Example I-4

Into a nickel-lined tank reactor were fed 2283 g (10 mol) of bisphenolA, 8400 g (10 mol) of 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane,4391.5 g (20.5 mol) of diphenyl carbonate, 2.9 mg (1.44×10⁻⁵ mol) ofsodium diborate, 48.9 mg (4×10⁻⁴ mol) of N,N-dimethyl-4-aminopyridineand 19.8 g (0.1 mol) of phenyl benzoate. A polycondensation was effectedin the same manner as that employed in Example I-1. Thus a colorless andtransparent reaction mixture comprising a copolycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thecopolycarbonate had a viscosity-average molecular weight (Mv) of 23,400and a terminal hydroxyl group concentration of 21 molar % based on allthe terminal groups of the copolycarbonate.

Comparative Example I-1

A polycondensation was effected under the same conditions as thoseemployed in Example I-1 except that no phenyl benzoate was added. Thus acolorless and transparent reaction mixture comprising a polycarbonatewas obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.10. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 29,000and a terminal hydroxyl group concentration of 52 molar % based on allthe terminal groups of the polycarbonate.

Comparative Example I-2

A polycondensation was effected under the same conditions as thoseemployed in Example I-2 except that no phenyl benzoate was added. Thus acolorless and transparent reaction mixture comprising a polycarbonatewas obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.13. Thepolycarbonate had a viscosity-average molecular weight (My) of 31,000and a terminal hydroxyl group concentration of 48 molar % based on allthe terminal groups of the polycarbonate.

Table 1 shows the results of the heat aging test (a) and the hydrolysistest performed with the use of the reaction mixtures obtained in theabove Examples I-1, I-2, I-3 and I-4 and Comparative Examples I-1 andI-2.

                  TABLE 1    ______________________________________    Ex.         Ex.     Ex.     Ex.   Comp.  Comp.    I-1         I-2     I-3     I-4   Ex. I-1                                             Ex. I-2    ______________________________________    Heat aging            0.05    0.07    0.04  0.05  0.34   0.88    test (a)    (t.sub.10)    Hydrolysis            0.03    0.01    0.03  0.04  0.31   0.73    test    ______________________________________

Example II-1

Into a glass flask were fed 22.8 g (0.1 mol) of2,2-bis(4-hydroxyphenyl)propane, 21.9 g (0.1025 mol) of diphenylcarbonate and 0.145 mg (7.2×10⁻⁷ mol) of sodium tetraborate. Aftermelting at 180° C. in a nitrogen atmosphere, the mixture was heatedwhile slowly reducing the pressure until the temperature and pressurefinally reached respectively 270° C. and 0.1 Torr under thoroughlystirring and polycondensation was effected under those conditions withthe removal of formed phenol by distillation. Thus a colorless andtransparent reaction mixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (My) of 29,000.

Example II-2

A polycondensation was effected under the same conditions as thoseemployed in Example II-1 except that 0.268 mg (7.2×10⁻⁷ mol) ofpotassium octaborate was used as the transesterification catalystinstead of the sodium tetraborate. Thus a colorless and transparentreaction mixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.08. Thepolycarbonate had a viscosity-average molecular weight (My) of 28,000.

Example II-3

A polycondensation was effected under the same conditions as thoseemployed in Example II-1 except that 2.4 mg (2×10⁻⁵ mol) ofN,N-dimethyl-4-aminopyridine as the transesterification catalyst wasfurther added. Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 28,500.

Example II-4

Into a glass flask were fed 11.4 g (0.05 mol) of2,2-bis(4-hydroxyphenyl)propane, 17.0 g (0.05 mol) of2,2-bis(4-hydroxy-8-tert-butylphenyl)propane, 22.5 g (0.105 mol) ofdiphenyl carbonate, 0.097 mg (5×10⁻⁷ mol) of sodium diborate and 0.068 g(1×10⁻³ mol) of imidazole. A polycondensation was effected in the samemanner as that employed in Example II-1. Thus a colorless andtransparent reaction mixture comprising a copolycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thecopolycarbonate had a viscosity-average molecular weight (Mv) of 23,400.

Comparative Example II-1

A polycondensation was effected under the same conditions as thoseemployed in Example II-1 except that 0.040 mg (7.2×10⁻⁷ mol) ofpotassium hydroxide was used as the transesterification catalyst insteadof the sodium tetraborate. Thus a colorless and transparent reactionmixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (My) of 25,000.

Comparative Example II-2

A polycondensation was effected under the same conditions as thoseemployed in Example II-1 except that 0.041 mg (5×10⁻⁷ mol) of sodiumacetate was used as the transesterification catalyst instead of thesodium tetraborate. Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 25,000.

Table 2 shows the results of the heat aging test (a) and the hydrolysistest performed with the use of the reaction mixtures obtained in theabove Examples II-1, II-2, II-8 and II-4 and Comparative Examples II-1and II-2.

As Table 2 shows, it was confirmed that the polycarbonates prepared inComparative Examples II-1 and II-2 were decomposed in the heat agingtest (a) and the hydrolysis test.

                  TABLE 2    ______________________________________           Ex.  Ex.    Ex.    Ex.  Comp. Ex.                                           Comp. Ex.           II-1 II-2   II-3   II-4 II-1    II-2    ______________________________________    Heat aging             0.05   0.06   0.04 0.05 0.86    1.12    test (a)    (t.sub.10)    Hydrolysis             0.03   0.02   0.03 0.04 0.76    0.88    test    ______________________________________

Example III-1

Into a glass flask were fed 22.8 g (0.1 mol) of2,2-bis(4-hydroxyphenyl)propane, 21.9 g (0.1025 mol) of diphenylcarbonate and an aqueous solution of 0.085 mg (1×10⁻⁵ mol) of lithiummetaborate dihydrate. After melting at 180° C. in a nitrogen atmosphere,the mixture was heated while slowly reducing the pressure until thetemperature and pressure finally reached respectively 270° C. and 0.1Torr under thoroughly stirring and polycondensation was effected underthose conditions with the removal of formed phenol by distillation. Thusa colorless and transparent reaction mixture comprising a polycarbonatewas obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.07. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 29,500.

Example III-2

A polycondensation was effected under the same conditions as thoseemployed in Example III-1 except that 0.268 mg (7.2×10⁻⁷ mol) ofpotassium octaborate was used as the transesterification catalystinstead of the lithium metaborate dihydrate. Thus a colorless andtransparent reaction mixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.08. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 30,000.

Example III-3

A polycondensation was effected under the same conditions as thoseemployed in Example III-1 except that 0.145 mg (7.2×10⁻⁷ mol) of sodiumtetraborate was used as the transesterification catalyst instead of thelithium metaborate dihydrate. Thus a colorless and transparent reactionmixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.11. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 24,000.

Example III-4

A polycondensation was effected under the same conditions as thoseemployed in Example III-1 except that 2.4 mg (2×10⁻⁵ mol) ofN,N-dimethyl-4-aminopyridine as the transesterification catalyst wasfurther added. Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 33,000.

Example III-5

Into a glass flask were fed 11.4 g (0.05 mol) of2,2-bis(4-hydroxyphenyl)propane, 17.0 g (0.05 mol) of2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, 22.5 g (0.105 mol) ofdiphenyl carbonate, 0.268 mg (7.2×10⁻⁷ mol) of potassium octaborate and0.068 g (1×10⁻³ mol) of imidazole. A polycondensation was effected inthe same manner as that employed in Example III-1. Thus a colorless andtransparent reaction mixture comprising a copolycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.09. Thecopolycarbonate had a viscosity-average molecular weight (Mv) of 23,400.

Comparative Example III-1

A polycondensation was effected under the same conditions as thoseemployed in Example III-1 except that 0.040 mg (7.2×10⁻⁷ mol) ofpotassium hydroxide was used as the transesterification catalyst insteadof the lithium metaborate dihydrate. Thus a colorless and transparentreaction mixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.10. Thepolycarbonate had a viscosity-average molecular weight (Mv) of 25,000.

Comparative Example III-2

A polycondensation was effected under the same conditions as thoseemployed in Example III-1 except that 0.041 mg (5×10³¹ 1 mol) of sodiumacetate was used as the transesterification catalyst instead of thelithium metaborate dihydrate. Thus a colorless and transparent reactionmixture comprising a polycarbonate was obtained.

The hue value (A₃₈₀ -A₅₈₀) of the reaction mixture was 0.10. Thepolycarbonate had a viscosity-average molecular weight (My) of 25,000.

Table 3 shows the results of the heat aging test (a) and the hydrolysistest performed with the use of the reaction mixtures obtained in theabove Examples III-1, III-2, III-3, III-4 and III-5 and ComparativeExamples III-1 and III-2.

As Table 3 shows, it was confirmed that the polycarbonates prepared inComparative Examples III-1 and III-2 were decomposed in the heat agingtest (a) and the hydrolysis test.

                  TABLE 3    ______________________________________    Ex.      Ex.    Ex.    Ex.  Ex.  Comp. Ex.                                             Comp. Ex.    III-1    III-2  III-3  III-4                                III-5                                     III-1   III-2    ______________________________________    Heat  0.03   0.03   0.05 0.04 0.04 0.86    1.12    aging    test (a)    (t.sub.10)    Hydro-          0.03   0.02   0.04 0.03 0.04 0.76    0.88    lysis    test    ______________________________________

Example IV-1

Into a nickel-lined tank reactor were fed 4560 g (20 mol) of2,2-bis(4-hydroxyphenyl)propane, 4391.5 g (20.5 mol) of diphenylcarbonate, 38 mg (1×10⁻⁴ mol) of sodium tetraborate and 30.9 mg (5×10⁻⁴mol) of boric acid. After melting at 160° C. and stirring for 1 hour ina nitrogen atmosphere, the mixture was heated while slowly reducing thepressure until the temperature and the pressure finally reachedrespectively 270° C. and 1 Torr and polycondensation was effected for 4hours under stirring under those conditions with the removal of formedphenol by distillation. The reaction mixture was further reacted in avertical, double-screw, self-cleaning reactor under 0.1 Torr and 280° C.for 50 minutes with the removal of formed phenol. Thus a colorless andtransparent reaction mixture comprising a polycarbonate was obtained.

The polycarbonate had a viscosity-average molecular weight (My) of35,000 and a terminal hydroxyl group concentration of 18 molar % basedon all the terminal groups of the polycarbonate.

Example IV-2

A polycondensation was effected in the same manner as that employed inExample IV-1 except that 489 mg (4×10⁻³ mol) ofN,N-dimethyl-4-aminopyridine was used as the transesterificationcatalyst instead of the sodium tetraborate and that the amount of theboric acid used was 1.2366 g (2×10⁻² mol). Thus a colorless andtransparent reaction mixture comprising a polycarbonate was obtained.

The polycarbonate had a viscosity-average molecular weight (Mv) of29,000 and a terminal hydroxyl group concentration of 18 molar % basedon all the terminal groups of the polycarbonate.

Example IV-3

Into a glass flask were fed 22.8 g (0.1 mol) of2,2-bis(4-hydroxyphenyl)propane, 21.96 g (0.1025 mol) of diphenylcarbonate, 2×10⁻⁵ g [5×10⁻⁶ mol/1 mol of the2,2-bis(4-hydroxyphenyl)propane] of lithium hydroxide monohydrate and1×10⁻³ g (1.6×10⁻⁵ mol) of boric acid. After melting at 180° C. andstirring for 1 hour in a nitrogen atmosphere, the mixture was heatedwhile slowly reducing the pressure until the temperature and thepressure finally reached respectively 270° C. and 0.1 Torr andpolycondensation was effected for 1 hour under stirring under thoseconditions with the removal of formed phenol by distillation. Thus acolorless and transparent reaction mixture comprising a polycarbonatewas obtained.

The polycarbonate had a viscosity-average molecular weight (My) of27,600, a terminal hydroxyl group concentration of 28 molar % based onall the terminal groups of the polycarbonate and a glass transitionpoint of 150° C.

Example IV-4

Into a glass flask were fed 22.8 g (0.1 mol) of2,2-bis(4-hydroxyphenyl)propane, 21.96 g (0.1025 mol) of diphenylcarbonate, 01.00122 g [1×10⁻⁴ mol/1 mol of the2,2-bis(4-hydroxyphenyl)propane] of N,N-dimethyl-4-aminopyridine,0.000042 g [1×10⁻⁵ mol/1 mol of the 2,2-bis(4-hydroxyphenyl)propane] oflithium hydroxide and 3.5 mg (5.7×10⁻⁵ mol) of boric acid. After meltingat 180° C. and stirring for 1 hour in a nitrogen atmosphere, the mixturewas heated while slowly reducing the pressure until the temperature andthe pressure finally reached respectively 270° C. and 0.1 Tort andpolycondensation was effected for 1 hour under stirring under thoseconditions with the removal of formed phenol by distillation. Thus acolorless and transparent reaction mixture comprising a polycarbonatewas obtained.

The polycarbonate had a viscosity-average molecular weight (My) of27,600, a terminal hydroxyl group concentration of 28 molar % based onall the terminal groups of the polycarbonate and a glass transitionpoint of 150° C.

Example IV-5

A polycondensation was effected in the same manner as that employed inExample IV-1 except that 489 mg (4×10⁻³ mol) ofN,N-dimethyl-4-aminopyridine was used as the transesterificationcatalyst instead of the sodium tetraborate and that 1.98 g (2×10⁻² mol)of ammonium hydrogenphosphite was used as the acidic substance insteadof the boric acid. Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The polycarbonate had a viscosity-average molecular weight (My) of26,000 and a terminal hydroxyl group concentration of 23 molar % basedon all the terminal groups of the polycarbonate.

Example IV-6

A polycondensation was effected in the same manner as that employed inExample IV-1 except that the amount of the boric acid used was 1.5458 g(2.5×10⁻² mol). Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The polycarbonate had a viscosity-average molecular weight (Mv) of26,700 and a terminal hydroxyl group concentration of 6 molar % based onall the terminal groups of the polycarbonate.

Example IV-7

A polycondensation was effected in the same manner as that employed inExample IV-2 except that the amount of the boric acid used was 12.866 g(2×10⁻¹ mol). Thus a colorless and transparent reaction mixturecomprising a polycarbonate was obtained.

The polycarbonate had a viscosity-average molecular weight (Mv) of24,600 and a terminal hydroxyl group concentration of 14 molar % basedon all the terminal groups of the polycarbonate.

Table 4 shows the results of the heat aging tests performed with the useof the reaction mixtures obtained in the above Examples IV-1, IV-2,IV-3, VI-4, IV-5, IV-6 and IV-7.

                                      TABLE 4    __________________________________________________________________________                    Ex.                       Ex. Ex.                              Ex. Ex.                                     Ex. Ex.                    IV-1                       IV-2                           IV-3                              IV-4                                  IV-5                                     IV-6                                         IV-7    __________________________________________________________________________    Heat aging          no. of cleavages                    0.01                       0.03                           -- --  0.08                                     0.03                                         0.02    test (a)          after 10 days (t.sub.10)          no. of cleavages                    0.05                       0.06                           -- --  0.10                                     0.08                                         0.08          after 20 days (t.sub.20)          no. of cleavages                    0.05                       0.08                           -- --  0.10                                     0.09                                         0.09          after 30 days (t.sub.30)    Heat aging          initial hue (YI)                    1.0                       1.0  1.5                               1.5                                  1.4                                     1.2 1.2    test (b)          hue after storage                    12 12  10.8                              11.3                                  14 14  14          (YI)    __________________________________________________________________________

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What we claim is:
 1. In a process for producing a (co)polycarbonate by the melt polycondensation of a dihydroxy compound with a carbonic diester, the improvement comprising conducting said melt polycondensation at a temperature of 100°-300° C. and a pressure of atmospheric to 0.1 Torr in the presence of an acidic substance selected from the group consisting of boric acid, ammonium hydrogenphosphite and a mixture thereof and a basic transesterification catalyst selected from the group consisting of a metal salt of boric acid, a nitrogen-containing basic compound, an electron donor amine compound, a salt of an electron donor amine compound, an alkali metal compound, an alkaline earth metal compound, a mixture of a nitrogen-containing basic compound and an alkali metal compound and a mixture of a nitrogen containing basic compound and an alkaline earth metal compound, said basic catalyst and the acidic substance are employed at such a ratio that (1) total amount of the boron atom of the boric acid and the phosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times by mol the amount of the metal atom of the metal salt of boric acid, that (2) the total amount of the boron atom of the boric acid and the phosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times by mol the amount of the basic group of the nitrogen-containing basic compound, that (3) the total amount of the boron atom of the boric acid and the phosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times by mol that of the metal atoms of the alkali metal compound and the alkaline earth metal compound or that (4) the total amount of the boron atom of the boric acid and the phosphorus atom of the ammonium hydrogenphosphite is 0.01 to 500 times by mol that of the basic group of the nitrogen-containing basic compound and the metal atoms of the alkali metal compound and the alkaline earth metal compound.
 2. The process for producing a (co)polycarbonate as claimed in claim 1, wherein the boric acid and/or ammonium hydrogenphosphite is added to the reaction system before the initiation of the polycondensation or during the initial stages of the polycondensation.
 3. The process for producing a (co)polycarbonate as claimed in claim 1 wherein the basic catalyst is a metal salt of boric acid.
 4. The process for producing a (co)polycarbonate as claimed in claim 1 wherein the basic catalyst is a nitrogen-containing basic compound.
 5. The process for producing a (co)polycarbonate as claimed in claim 1 wherein the basic catalyst is an electron doner amine compound or a salt thereof.
 6. The process for producing a (co)polycarbonate as claimed in claim 1 wherein the basic catalyst is a compound selected form the group consisting of an alkali metal compound and an alkaline earth metal compound.
 7. The process for producing a (co)polycarbonate as claimed in claim 1 wherein the basic catalyst is a mixture of a nitrogen-containing basic compound and a compound selected form the group consisting of an alkali metal compound and an alkaline earth metal compound. 